Device for supporting a person

ABSTRACT

A support device has a main support surface for a person&#39;s body, including an auxiliary device influencing the main support surface shape. The auxiliary device includes: a group of supports supporting the main support surface, positioned on the side of the main support surface facing away from the body-supporting side, the supports each including a sub-support surface; an adjuster for each sub-support surface influencing the height of each sub-support surface. The device also includes a monitor for each sub-support surface monitoring the height of the respective sub-support surface; and a programmable control unit controlling the adjuster. The supports include an elastically bendable plate connected to the adjuster. The bending plate is connected to the sub-support surface to influence its height depending on the extent of bending imposed by the adjuster. The adjuster includes an electromotor on the concave side of the bending plate.

BACKGROUND OF THE INVENTION

The invention relates to a device for supporting persons. The person using the device can be supported while sitting or recumbent. A field of application of the invention is aimed at improving the comfortableness of the person in question, in particular when the person needs to be supported for a long period of time, such as in the transport sector, in particular truck drivers and couriers. Another field of application is aimed at medical effects, in particular counteracting decubitus (bedsores), such as for sitting or recumbent persons. Another field of application is occupational therapy.

It is known to design such a device, intended for one or more of the above-mentioned applications, with a primary or main support surface/contact surface for a person's body, and with a group of support elements positioned below the main support surface and each defining a secondary or sub-support surface on which the main support surface supports. By adjusting the height of each of the sub-support surfaces in a controlled manner, the shape of the main support surface can be influenced while the person sits or lies on it.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a support device of the type mentioned in the preamble with which an accurate local setting of the shape of the support surface for the user is possible.

It is an object of the invention to provide a support device of the type mentioned in the preamble with which, considered in the vertical sense, the shape of the support surface for the user can be adjusted to a large extent to the actual situation.

It is an object of the invention to provide a support device of the type mentioned in the preamble which can be compact in the vertical sense.

It is an object of the invention to provide a support device of the type mentioned in the preamble with which an accurate distribution of the forces exerted thereon by the user can be achieved.

According to one aspect the invention provides a support device having a main support surface for the body of a person, comprising an auxiliary device for influencing the shape of the main support surface, wherein the auxiliary device comprises:

-   -   a group of support elements for supporting the main support         surface, which group is positioned on the side of the main         support surface that faces away from the body-supporting side,         wherein the support elements each comprise a sub-support         surface,     -   adjustment means for each sub-support surface for influencing         the height of each sub-support surface relative to a reference         plane and consequently the local height of the main support         surface,     -   monitoring means for each sub-support surface for monitoring the         height of the respective sub-support surface relative to the         reference plane and/or the force exerted on the respective         sub-support surface by the person, and     -   a programmable control unit for controlling the adjustment means         in response to data received from the monitoring means,     -   wherein the support elements each comprise an elastically         bendable plate (bending plate) that is connected to the         adjustment means so as to be influenced thereby in its extent of         bending,     -   wherein the bending plate is connected to the sub-support         surface in order to influence its height depending on the bent         condition as imposed by the adjustment means, wherein the         adjustment means each comprise an electromotor that is situated         on the concave side of the bending plate.

The support device according to the invention provides the possibility of adjusting either the shape of the main support surface, or the distribution of the forces exerted on it by the user, in response to the actual condition. The combination of adjustment means and electromotor, which preferably is a stepper motor, for each sub-support surface, the monitoring means and the bending plates make it possible to influence, in particular adjust the sub-support surfaces and consequently the main support surface, accurately. The occupation of space in the vertical sense can then be kept limited as the electromotor and the bending plate in the vertical sense can at least partially coincide, the electromotor can at least be partially surrounded by the bending plate, as it were. In one embodiment, the bending plate is positioned with the concave side at its bottom side.

Accurate influencing, in particular adjustment, can be furthered if the support elements each comprise two bending plates situated one above the other, which face each other with their concave sides, wherein the electromotor is situated between both bending plates. In that case the electromotor adds no constructional height to the support element.

In a compact embodiment the electromotor is attached to one end of the bending plate or to adjacent ends of both bending plates to be jointly displaced with them,

-   -   wherein the adjustment means furthermore comprise a drive member         that is driven by the electromotor and at one end is connected         in a driving fashion to the other end of the bending plate or         the other ends of both bending plates. The drive member can then         be a shaft, such as a spindle, which is linearly moved by the         electromotor, in particular step-wise (stepper motor).

In a further development of the support device according to the invention it comprises a frame and

-   -   bending elements that are elastically bendable in the vertical         plane and by means of which the respective support elements are         attached to the frame,     -   wherein the monitoring means comprise sensors for monitoring the         bend of the bending elements and/or the force the user exerts on         the bending elements,     -   wherein the sensors are connected to the control unit for giving         it signals that are indicative of the bend of the bending         elements and/or the force exerted on the bending elements,     -   wherein the control unit is configured for on the basis of the         signals received from the sensors calculating the vertical         position of the support element and/or the force exerted on the         bending elements. The bending elements deform as a result of the         load on the respective support elements and in addition to a         support function to the support elements also have a function in         providing information about the forces that arise.

In a simple and reliably functioning embodiment, the bending elements each comprise an elastically bendable beam,

-   -   wherein the sensors each comprise a resistance strain gauge         disposed on the beam.

In a further development thereof, the beam is clamped at one end and free at the other end.

In one embodiment, in which the support elements are provided with a bending plate on one side of the electromotor only, the electromotor is attached to the beam.

In an alternative embodiment, in which the support element comprises a bending plate on one side of the electromotor only, that support plate is attached to the beam. In the case of support plates on both sides of the electromotor, the support plate which is situated on one of either sides of the electromotor can be attached to the beam.

In a space-saving embodiment the location of attachment is in the center (the longitudinal center between both ends) of the respective bending plate.

In case of a cantilever beam, the location of attachment can be at the free end of the beam, as a result of which the displacement under vertical force is as large as possible, which can be conducive to a fine-tuning.

In one embodiment, the bending plate is, or both bending plates are, positioned such that the horizontal distance between both ends of each bending plate is changed when the respective bending plate bends. The center of each bending plate is then vertically displaced upon bending.

For each support element a stop can be arranged for limiting the vertical downward travel of the bending element.

The sub-support surface can be integrally formed with the bending plate.

In a further development, the sub-support surface of each support element is flat, in particular in the horizontal plane. That way the curvature of a bending plate of which the convex side is facing upward, can be made less noticeable to a person supported on the main support surface. The flat sub-support surface can be integrally formed with the respective bending plate. Alternatively, the flat sub-support surface can be part of a small plate added to the respective bending plate, which small plate preferably is attached to the bending plate in a relatively movable fashion. The small plate can then be attached to the respective bending plate so as to hinge, preferably so as to hinge in all directions (universally), such as with a ball hinge. The small plate is then in body-tracing position, which may be pleasant to the user.

According to a further aspect the invention provides a support device having a main support surface for the body of a person, comprising an auxiliary device for influencing the shape of the main support surface, wherein the auxiliary device comprises:

-   -   a group of support elements for supporting the main support         surface, which group is positioned on the side of the main         support surface that faces away from the body-supporting side,     -   wherein the support elements each comprise a sub-support         surface,     -   adjustment means for each sub-support surface for influencing         the height of each sub-support surface relative to a reference         plane and consequently the local height of the main support         surface,     -   monitoring means for monitoring a parameter that is indicative         of the force exerted on each sub-support surface by the person,         and     -   a programmable control unit that is connected to the monitoring         means for receiving the data regarding the respective parameter,     -   wherein the control unit is configured for:     -   on the basis of the data received from the monitoring means         calculating the individual force F1, F2, . . . , Fn exerted on         each sub-support surface by the person,     -   calculating the average “Fmean” of the calculated forces F1, F2,         . . . Fn,     -   comparing the calculated forces F1, F2, . . . Fn to the         calculated Fmean, and     -   on the basis of the outcome of said comparison, controlling the         adjustment means to change the height of the respective         sub-support surface in order to, in case of a difference between         the calculated individual force on a sub-support surface and the         calculated Fmean, reduce that difference. The average “Fmean”         can be determined as arithmetic average.

In one embodiment, only those sub-support surfaces that the person actually places a load on, in other words the active support elements, are included in the calculations.

In one embodiment, the control unit is configured for repeatedly receiving from the monitoring means, the data for each of the support elements of which the adjustment means are controlled, and each time on the basis of those data calculating the force exerted on the sub-support surface and then once more calculating the average force and making the said comparison, and subsequently on the basis of the outcome of said comparison controlling the adjustment means once more. This amounts to a control system in which the sub-support surfaces are adjusted in height stepwise and the effect adjustment of the one sub-support surface has on the loading of the other sub-support surfaces is taken into account. Ultimately, it is possible to approximate a situation in which the person exerts the same force on each sub-support surface.

In one embodiment the control unit is configured for allowing the user to make a selection of the support elements that do or do not have to be controlled by the control unit during use. The control unit can then be configured for putting the support elements selected not to be controlled, in the lowest position, at least in a low position as a result of which they will be able to remain free from being loaded by the user. For instance, a user wishing to off-load a particular part of his body, such as may for instance be the case when the user has a bedsore, can place the support elements that would otherwise provide support to the area of that spot in the lowest position in order to ensure that during use that area will not or hardly be loaded. When the user usually seats himself on one and the same chair and usually takes up the same position and place, this may be an advantageous option.

In one embodiment, the control unit is configured for also after to an at least acceptable extent achieving an evenly distributed load, continuing the said control process, to detect the person's displacement relative to the sub-support surfaces and controlling the adjustment means accordingly to a new roughly evenly distributed loaded condition of the sub-support surfaces.

As described above, the support elements can each comprise an elastically bendable plate that is connected to the adjustment means to be adjusted thereby in its the extent of bending,

-   -   wherein the bending plate is connected to the sub-support         surface to influence its height depending on the extent of         bending.

In this case as well the adjustment means can each comprises an electromotor that is situated on the concave side of the bending plate.

According to a further aspect, the support device can be equipped with one or more of the features described in claims 1-19.

According to a further aspect, the invention provides a method for influencing the shape of a main support surface of a support device for a person, using an auxiliary device for influencing the shape of the main support surface, which auxiliary device comprises:

-   -   a group of support elements for supporting the main support         surface, which group is positioned on the side of the main         support surface that faces away from the body-supporting side,     -   wherein the support elements each comprise a sub-support         surface,     -   wherein adjustment means are present for each sub-support         surface for influencing, in particular adjusting, the height of         each sub-support surface relative to a reference plane and         consequently the local height of the main support surface; which         adjustment means are operable by a programmable control unit,     -   wherein the shape of the main support surface is influenced by         influencing, in particular adjusting, the height of at least a         number of the sub-support surfaces relative to a reference plane         and consequently the local height of the main support surface,     -   wherein the method comprises the following steps:         a) allowing the control unit to operate the adjustment means for         bringing each sub-support surface in a predetermined position;         b) allowing a person to take place on the main support surface;         c) after a period of time, for instance 10 seconds, per         sub-support surface calculating the (actual) forces F1, F2, . .         . Fn the person exerts on each of the sub-support surfaces;         d) calculating the average “Fmean” of the calculated forces F1,         F2, . . . Fn,         e) comparing the calculated forces F1, F2, . . . Fn to the         calculated Fmean, and         f) on the basis of the outcome of said comparison, controlling         the adjustment means to change the height of the respective         sub-support surface in order to, in case of a difference between         the calculated individual force on a sub-support surface and the         calculated Fmean, reduce that difference. The average “Fmean”         can be determined as arithmetic average.

The series of steps c)-f) can be carried out repeatedly, with short intervals that are in the order of (for instance a part of a second) the period of time required for measuring, calculating and operating the adjustment means, which adjustment means preferably comprise a stepper motor. Said intervals can be a part of a second. Ultimately, a situation could then be achieved in which all loaded support elements are roughly evenly loaded. Pressure peaks can be prevented.

In one embodiment, the series of steps c)-f) are carried out for as long as the person is supported on the main support surface. That way a change in the posture and/or position of the person can be anticipated. A delay may have been set, for instance of a few seconds, in order for the system not to seem too unquiet to the user.

In one embodiment, in step c) only the actual force exerted on the sub-support surfaces that are used by the person is calculated. When changing position that may be a different group than previously.

In one embodiment, in step a) the sub-support surfaces are set at equal height. This may be a height in between the maximum and minimum height.

In one embodiment, prior to step c), in particular prior to step b), the user makes a selection of the support elements that do or do not need to be controlled by the control unit during use. The user can then direct the control unit to place support elements selected not to be controlled in the lowest position. Those will not be loaded by the user's body, which may be advantageous when the user wishes to off-load a possible support surface of his body.

In the method according to the invention, advantageous use can be made of a support device according to the invention as described above and/or in the attached claims.

The aspects and measures described in this description and the claims of the application and/or shown in the drawings of this application may where possible also be used individually. Said individual aspects may be the subject of divisional patent applications relating thereto. This particularly applies to the measures and aspects that are described per se in the sub claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which:

FIG. 1 shows a wheelchair provided with a seat cushion in which the support device according to the invention is incorporated;

FIGS. 2A and 2B show an isometric view diagonally from above of a support device according to the invention and a side view of it, with addition, respectively;

FIGS. 3A-F show three views of the support element of the support device of FIGS. 2A and 2B in different views and in different conditions, respectively;

FIG. 4 shows a schematic view of a bending plate of a support element, in an alternative embodiment; and

FIG. 5 shows a flow chart of an example of the user process of a support device according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The wheelchair 1 in FIG. 1 is an example of an application of a support device according to the invention. The support device according to the invention can be used in any situation in which a person needs to be supported in the sitting or recumbent position: both in chairs and in beds.

The wheelchair 1 comprises a frame 2 supported by wheels, on which frame a backrest 3 and a seat 4 are arranged. On the seat 4 a cushion 5 is placed, in which an example of a support device 10 according to the invention is incorporated.

In FIGS. 2A and 2B the support device 10 is shown in further detail. The support device 10 comprises a group of support elements 6 that are positioned in a number of series, wherein the consecutive series are shifted relative to each other along half a length of the support element 6. The group of support elements is surrounded all around by a band 8 of synthetic foam, of which only two sides are shown. The support elements 6 are attached to a rigid base plate 40 on which slightly above it a printed circuit board 41 including connections 42 is also situated. At their top sides, the support elements 6 each form a sub-support surface 7, wherein the sub-support surfaces 7 are covered by a layer of foam rubber 30 and the whole is surrounded by an enveloping 31, see FIG. 2B, which enveloping forms a main support surface. The main support surface and the layer of foam rubber is supported on the sub-support surface. The support device is provided with a programmable control unit 100, provided with a power source, such as a battery.

A support element 6 is shown in further detail in FIGS. 3A-C. The support element 6 comprises two elastically bendable bending plates 9 a, 9 b, which are bent upward and downward, respectively, in a convex fashion. The bending plates 9 a,b can be manufactured of synthetic material, such as a nylon. A space A is formed between concave sides of the bending plates 9 a,b, in which space an electromotor is accommodated, in the example stepper motor 14. The stepper motor 14, which is connected to a connector 42 on the printed circuit board 41 via wiring 26 and to the control unit 100 via the printed circuit board 41, is attached to a cut-away housing 16, and drives a shaft 15 in horizontal directions B1,2. The end 15 a of the shaft 15 is attached in an end block 18, with which the beaded edge-shaped ends 19 a of the bending plate 9 a and the beaded edge-shaped ends 19 b of the bending plate 9 b are connected so as to hinge in the vertical plane. The other ends of the bending plates 9 a and 9 b are similarly connected to the end block 17 which is integral with the housing 16.

In its center, the lowermost bending plate 9 b (considered both in the longitudinal direction and in the width direction) is attached by a bolt connection 20 near the free end of a flat, beam 21 clamped on one side, which beam is elastically bendable in the vertical plane. At the other end, the beam 21 is attached to a support block 23 in a rigidly clamped fashion by means of screws 24, which support block is rigidly attached to the rigid plate 40.

The bolt connection 20 has a head 20 a extending downward, which is situated above a stop (not shown) that is attached to the plate 40 and extends upwards therefrom. This stop limits the downward displacement of the free end of the beam 21.

A resistance strain gauge 22 is arranged on the beam 21, which gauge is connected to a connector 42 on the printed circuit board 41 via wiring 25, and to the control unit 100 via the printed circuit board 41.

In FIGS. 3D-F it is shown how by means of operating the support elements 6 by the control unit 100, the vertical distance between the top and bottom of the bending plate 9 a and bending plate 9 b, respectively, can be influenced. In FIG. 3D the shaft 15 is fully retracted in direction B2 into the stepper motor 14. The height h3 of the support element 6 is then at its maximum. When the stepper motor 14 extends the shaft 15 (direction B1) the horizontal distance between the end blocks 17 and 18 will be increased, as a result of which the height h2 of the support element 6 decreases, see FIG. 3E. When the shaft 15 has been extended to its maximum, FIG. 3F, the height h1 is at its minimum. When the shaft 15 is retracted (direction B2) the height will increase again.

FIG. 4 shows an embodiment of the bending plate 9 a, in which the sub-support surface 7 is formed by a small flat plate 50, which at the bottom side is provided with a bearing ball 51, that is accommodated so as to be rotatable, directions C, in bearing cavity 52, that is integrally formed with the bending plate 9 a.

In actual practice, once a user has left the support device, for instance placed on the wheelchair of FIG. 1, and the support device therefore is not loaded, the control unit 100 will control the stepper motors 14 of all support elements 6 into a retracted position of the shafts 15. In the control unit the related condition of the resistance strain gauges 22 is stored as zero-setting. The support device has then been calibrated or “zeroed”, also see the chart in FIG. 5. Zeroing or calibrating is also possible by fully extending all shafts. The control unit 100 will subsequently control the stepper motors 14 for extending the shafts 15 to half an extension length. The support device is then ready for use.

When the user takes his seat on the support surface, a force exerted by the user's body on the one support element 6 will be larger than on the other support element. Some support elements, especially those at the edges of the support device, will not be loaded.

The load on the support elements 6 will result in the respective beam 21 bending through, causing a change in the condition of the resistance strain gauge 22 attached to it. This change is detected in the control unit 100, which by using the data of the resistance strain gauge calculates the force exerted on the beam 21. This is done for all loaded support elements. The control unit 100 subsequently calculates the arithmetic average value of those forces.

In the control unit 100, the force F1, F2, . . . Fn calculated for each loaded support element is then compared to the calculated average force Fmean (in the figure called Fm). If the outcome is that the force on the support element exceeds Fmean, then the stepper motor for that support element is controlled so as to extend the shaft one step, for instance 2 mm. As a consequence the convexity of both bending plates 9 a,b will decrease, as a result of which the sub-support surface 7 of that support element 6 will come to lie lower. If the outcome is that the force on the support element is smaller than Fmean, then the stepper motor for that support element is controlled so as to retract the shaft one step. As a consequence the convexity of both bending plates 9 a,b will increase, as a result of which the sub-support surface 7 of that support element 6 will come to lie higher. On the sub-support surfaces then adjusted lower, the force exerted by the user will become lower, and on the sub-support surfaces adjusted higher it will indeed increase. After this measuring and calculation step and adjustment step, the process is repeated over and over again until F1, F2 . . . Fn roughly equal Fmean.

Subsequently, with the user on the support device, said steps are continuously carried out, so that a change of posture of the user can remain without adverse effects.

Controlling the electromotors 14 of the support elements 6 after the step of comparing the calculated forces F1, F2 . . . Fn to the Fmean, may in one embodiment take place in groups, such as that the wanted support elements of a first group of adjacent support elements are first operated and subsequently the wanted support elements of a second group, etc. This can be done in quick succession. The power required can be kept limited, which is advantageous when using a battery for the power supply of the electromotors.

The invention is/inventions are not at all limited to the embodiments described in the description and shown in the drawings. The above description is included to illustrate the operation of preferred embodiments of the invention and not to limit the scope of the invention. Starting from the above explanation many variations that fall within the spirit and scope of the present invention will be evident to an expert. Variations of the parts described in the description and shown in the drawings are possible. They can be used individually in other embodiments of the invention(s). Parts of the various examples given can be combined together. 

1. A support device having a main support surface for the body of a person, comprising an auxiliary device for influencing the shape of the main support surface, wherein the auxiliary device comprises: a group of support elements for supporting the main support surface, which group is positioned on the side of the main support surface that faces away from the body-supporting side, wherein the support elements each comprise a sub-support surface, an adjustment device for each sub-support surface for influencing the height of each sub-support surface relative to a reference plane and consequently the local height of the main support surface, the support device comprising: a monitoring device for each sub-support surface for monitoring the height of the respective sub-support surface and/or the force exerted on the respective sub-support surface by the person, and a programmable control unit for controlling the adjustment devices in response to data received from the monitoring devices, wherein the support elements each comprise an elastically bendable plate that is connected to the adjustment device so as to be influenced thereby in its extent of bending, wherein the bending plate is connected to the sub-support surface in order to influence its height depending on the extent of bending imposed by the adjustment device, wherein the adjustment devices each comprise an electromotor that is situated on the concave side of the bending plate.
 2. The support device according to claim 1, wherein the support elements each comprise two bending plates situated one above the other, which face each other with their concave sides, wherein the electromotor is situated between both bending plates.
 3. The support device according to claim 1, wherein the electromotor is attached to one end of the bending plate or to adjacent ends of both bending plates to be jointly displaced with them, wherein the adjustment device furthermore comprise a drive member that is driven by the electromotor and with one end is connected in a driving fashion to the other end of the bending plate or the other ends of both bending plates.
 4. The support device according to claim 3, wherein the drive member is a shaft that is linearly displaced by the electromotor.
 5. The support device according to claim 1, comprising a frame and bending elements that are elastically bendable in the vertical plane and by means of which the respective support elements are attached to the frame, wherein the monitoring devices comprise sensors for monitoring the bend of the bending elements and/or the force the user exerts on the bending elements, wherein the sensors are connected to the control unit for giving it signals that are indicative of the bend of the bending elements and/or the force the user exerts on the bending elements, wherein the control unit is configured for on the basis of the signals received from the sensors calculating the force exerted on the bending elements and associated vertical position of the support element.
 6. The support device according to claim 5, wherein the bending elements each comprise an elastically bendable beam, and wherein the sensors each comprise a resistance strain gauge disposed on the beam.
 7. The support device according to claim 6, wherein the beam is clamped at one end and free at the other end.
 8. The support device according to claim 6, wherein the support elements are provided with a bending plate on one side of the electromotor only, and wherein the electromotor is attached to the beam.
 9. The support device according to claim 6, wherein the support plate is attached to the beam.
 10. The support device according to claim 9, wherein the location of attachment is in the center of the respective bending plate.
 11. The support device according to claim 8, wherein the beam is clamped at one end and free at the other end and wherein the location of attachment is at the free end of the beam.
 12. The support device according to claim 1, wherein the bending plate is or both bending plates are positioned such that the horizontal distance between both ends of each bending plate is changed upon changing the extent of bending of bending plate in question.
 13. The support device according to claim 5, provided with a stop for limiting the vertical downward travel of the bending element.
 14. The support device according to claim 1, wherein the sub-support surface of each support element is flat.
 15. The support device according to claim 14, wherein the flat sub-support surface is integrally formed with the respective bending plate.
 16. The support device according to claim 14, wherein the flat sub-support surface is part of a small plate added to the respective bending plate, which small plate is hinged to the bending plate in a relatively movable fashion.
 17. (canceled)
 18. The support device according to claim 1, wherein the electromotor is a stepper motor.
 19. The support Support device according to claim 1, wherein of the bending plate which is connected to the sub-support surface and carried thereby, the concave side is the bottom side.
 20. Support device according to claim 1 comprising: monitoring devices for monitoring a parameter that is indicative of the force exerted on each sub-support surface by the person, and a programmable control unit that is connected to the monitoring devices for receiving the data regarding the parameter, wherein the control unit is configured for: on the basis of the data received from the monitoring devices calculating the individual force F1, F2, . . . , Fn exerted on each sub-support surface by the person, calculating the average “Fmean” of the calculated forces F1, F2, . . . Fn, comparing the calculated forces F1, F2, . . . Fn to the calculated Fmean, and on the basis of the outcome of said comparison, controlling the adjustment means to change the height of the respective sub-support surface in order to, in case of a difference between the calculated individual force on a sub-support surface and the calculated Fmean, reduce that difference. 21-31. (canceled)
 32. A method Method for influencing the shape of a main support surface of a support device for a person, using an auxiliary device for influencing the shape of the main support surface, which auxiliary device comprises: a group of support elements for supporting the main support surface, which group is positioned on the side of the main support surface that faces away from the body-supporting side, wherein the support elements each comprise a sub-support surface, wherein adjustment devices are present for each sub-support surface for influencing the height of each sub-support surface relative to a reference plane and consequently the local height of the main support surface; which adjustment devices are operable by a programmable control unit, wherein the shape of the main support surface is influenced by influencing the height of at least a number of the sub-support surfaces relative to a reference plane and consequently the local height of the main support surface, wherein the method comprises the following steps: a) allowing the control unit to operate the adjustment devices for bringing each sub-support surface in a predetermined position; b) allowing a person to take place on the main support surface; c) after a period of time, for instance 10 seconds, per sub-support surface calculating the (actual) forces F1, F2, . . . Fn the person exerts on each of the sub-support surfaces; d) calculating the average “Fmean” of the calculated forces F1, F2, . . . Fn, e) comparing the calculated forces F1, F2, . . . Fn to the calculated Fmean, and on the basis of the outcome of said comparison, controlling the adjustment means to change the height of the respective sub-support surface in order to, in case of a difference between the calculated individual force on a sub-support surface and the calculated Fmean, reduce that difference. 33-43. (canceled) 